FLOOD08771

• County: Moffat
• Community: Craig
• Stream Name: Brotherton, Cedar Mountain Gulches
• Basin: Yampa/White
• Title: Craig Hydrology with HEC1 Data
• Date: 3/29/1978
• Prepared For: US Army Corps of Engineers
• Prepared By: Gingery Associates, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

Gingery Associates, Ine.
CONSULTING ENGINEERS
2840 SOUTH VALLEJO STREET
ENGLEWOOD, COLORADO 801 10
TELEPHONE 303761,4860

ASSOCIATES
OCRYl W. GINGERY
ELMER L. CLAl'COMS
LAIIRY A. MULLER

BRANCH OFFICE
GLENWOOO SPRINGS.
COlORADO 8160J
:J03 945-8676 /1-:;(./4
March 29, 1978 'V7 7 (

Mr. Robert Kelly
U.S. Army Corps of Engineers
Sacramento District
650 Capitol Mall
Sacramento, California 95814

Dear Mr. Kelly:

Enclosed are the calculations used to update the Craig hydrology
on Brotherton and Cedar Mountain Gulches to reflect future develop-
ment. The information includes:

(1) New basin lag times with n = .05,
(2) Unit hydrograph calculations,

(3) A basin development: map,

) (4) New values of rainfall loss rates and initial rainfall loss,

~ HEC-l computer runs including separate streamflow routings, and

I (6) New frequency distributions for full development.

Discharges are generally 20 to 40 percent higher than those used
in your report. The 10 year flow on Brotherton Gulch is, however,
nearly equal to your 10 year flow. I feel this is the result of
the 10 year flood changing from a transition curve point to a
rainfall curve point on the frequency graph. I do not feel this
is a problem.

Please review these calculations and contact me if you have any
questions.

Thank you for your cooperation and assistance in providing informa-
tion during this study.

Sincerely,

~ Ct~'-i ~"-f'""tt:.-
r Ill' ~ .I
;'~" t-'\ ~\ ,{./) CUt.l,.........

GINGERY ASSOCIATES, INC.

0~f >>1~L

PFM:meo
Enclosure
cc: Messrs.

~k F. Mulhern

James pankonin, Moffat County
Mike Taylor, City of Craig
CIVil ENGINEERING I LAND SURVEYING f STORM DRAINAGE I STRUCTURH! TRANSPORTATION! WATER & SANITATION I COMPUTER SERVICES